The present invention relates to the food carrying apparatus and more particularly to a portable warm bag having steam heating device which is able to create steam circulating in the bag to heat the food to a desired temperature.
People are used to carry a portable warm bag containing food to go outdoor to sponsor a picnic or other activities. The food in the bag will be warm and eatable. FIG. 1 shows a prior art warm bag 10 which is made of heatproof material has a lid 11 connected with one edge of its opening and fastened by a zipper 13 and a suspender 12 connected with two lateral sides to facilitate the user to carry the bag 10. This type of warm bag 10 has at least the following disadvantages:                a) the heatproof effect is very pool. The temperature of the food in the bag can only keep few hours, especially in the winter time or snowing days, than the heatproof effect for food is rather worse it is no use for a worker, a student or a traveler,        b) in summer time, although the temperature of the food containing in this bag may keep a longer time, but if there is no any heating device in the bag to continuously heat the food which will be easily fermented and/or deteriorated that becomes not eatable.        
Some of the warm bags utilize the electricity to heat the food to keep the food at a constant temperature. Yet this type of warm bag has usually a large volume and the electricity is coming from an automobile which is unsuitable to a student or a worker because they need a small sized portable warm bag.